FAILED: patch "[PATCH] misc: fastrpc: Fix copy buffer page size" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x e966eae72762ecfdbdb82627e2cda48845b9dd66
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025021139-bounce-growl-6d4e@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e966eae72762ecfdbdb82627e2cda48845b9dd66 Mon Sep 17 00:00:00 2001
From: Ekansh Gupta <[email protected]>
Date: Fri, 10 Jan 2025 13:42:39 +0000
Subject: [PATCH] misc: fastrpc: Fix copy buffer page size

For non-registered buffer, fastrpc driver copies the buffer and pass it to the remote subsystem. There is a problem with current implementation of page size calculation which is not considering the offset in the calculation. This might lead to passing of improper and out-of-bounds page size which could result in memory issue. Calculate page start and page end using the offset adjusted address instead of absolute address.

index 56dc3b3a8940..7b7a22c91fe4 100644
@@ -1019,8 +1019,8 @@ static int fastrpc_get_args(u32 kernel, struct fastrpc_invoke_ctx *ctx)
 					(pkt_size - rlen);
 			pages[i].addr = pages[i].addr &	PAGE_MASK;
 
-			pg_start = (args & PAGE_MASK) >> PAGE_SHIFT;
-			pg_end = ((args + len - 1) & PAGE_MASK) >> PAGE_SHIFT;
+			pg_start = (rpra[i].buf.pv & PAGE_MASK) >> PAGE_SHIFT;
+			pg_end = ((rpra[i].buf.pv + len - 1) & PAGE_MASK) >> PAGE_SHIFT;
 			pages[i].size = (pg_end - pg_start + 1) * PAGE_SIZE;
 			args = args + mlen;
 			rlen -= mlen;